WELCOME to Science of Christmas, where we explore some of the magic and mystery of this very special time.

Many of the wonderful things that we associate with the festive season can be explained by the so-called "hard" sciences: we can thank physics for the delicate beauty of snowflakes.

But, more than anything, Christmas is a time of goodwill and so, it is the "soft sciences", those that touch on human behaviour, that build the warm atmosphere.

We are grateful to scientists in colleges all over the country, many of them funded by the Irish Research Council in pursuit of more knowledge for the benefit of society, for their contributions to this supplement.

Some questions are easier to answer than others. In some cases, science has not finished its work and in years to come we will know even more. That is what research is all about: wondering…. and then looking for an answer.

Sometimes, while waiting for the evidence, you have trust and believe.

Little Virginia O'Hanlon, from New York, was eight in 1897, and was worried when she heard some of her friends say there was no Santa Claus.

Her dad suggested she write to a local newspaper

No scientific breakthrough in the 117 years since Francis Pharcellus Church wrote his response, nor any modern newspaper editor, could have given her a better answer.

In the 100th anniversary of the first Christmas of the World War 1, it is especially appropriate to highlight a supreme example of the indomitable spirit of the season; soldiers from opposing sides on the Western Front calling a spontaneous truce.

All along No Man's Land, they emerged from the trenches, finding some solace as their voices joined in unison to sing 'Silent Night' and other carols.